This invention relates to glucagon-related peptides and their use for the prevention or treatment of disorders involving the large intestine.
Glucagon-like peptide-2 (GLP-2) is a 33 amino acid peptide expressed in a tissue-specific manner from the pleiotropic glucagon gene. GLP-2 shows remarkable homology in terms of amino acid sequence to glucagon and Glucagon-like peptide-1 (GLP-1). Further, different mammalian forms of GLP-2 are highly conserved. For example, the human GLP-2 (hGLP-2) and degu (a south American rodent) GLP-2 differ from rat GLP-2 (rGLP-2) by one and three amino acids respectively. When given exogenously, GLP-2 can produce a marked increase in the proliferation of small intestinal epithelium of the test mice, apparently with no undesirable side effects (Drucker et al., 1996, PNAS:USA, 93:7911-7916). Subsequently it was shown that peptide analogs of native GLP-2 with certain modifications to the peptide sequence possess enhanced intestinotrophic activity at the small intestine (see co-pending application U.S. Serial No. 08/669,791, incorporated herein by reference). Moreover, GLP-2 has also been shown to increase D-Glucose maximal transport rate across the intestinal basolateral membrane [Cheeseman and Tseng, 1996, American Journal of Physiology 271:G477-G482].
The invention is based, in part, on the discovery that GLP-2 receptor agonists act to enhance functioning of the large intestine. It is accordingly a general object of the present invention to exploit GLP-2 receptor agonists for therapeutic and related purposes.
In particular, it-has been demonstrated that GLP-2 and peptidic analogs of GLP-2 can cause proliferation of the tissue of large intestine. Thus, in one aspect the invention provides a method of proliferating the large intestine in a subject in need thereof comprising delivering to the large intestine of the subject a large intestine proliferating amount of GLP-2 or a GLP-2 analog. In a preferred embodiment, the GLP-2 analog is one that is resistant to cleavage by DPP-IV, e.g., human [Gly2]GLP-2 (referred to herein as [Gly2]hGLP-2).
More particularly, and according to one aspect of the invention, there is provided a method of treating a subject having an inflammatory condition of the intestine involving the large intestine, wherein GLP-2 or a GLP-2 analog is delivered to the large intestine in an amount capable of ameliorating the inflammation of the large intestine. In a preferred embodiment, the GLP-2 analog is one that is resistant to cleavage by DPP-IV, e.g., [Gly2]hGLP-2.
In a related aspect of the invention, there is provided a method of treating a subject having an inflamed large intestine comprising the step of delivering to the subject a large intestine inflammation ameliorating amount of GLP-2 or an analog of GLP-2 in a pharmaceutically or veterinarily acceptable carrier. In a further aspect, GLP-2 or an analog of GLP-2 is provided in a pharmaceutically or veterinarily acceptable form in an amount effective to cause proliferation of the large intestine. Preferably, the GLP-2 analog is one that is resistant to cleavage by DPP-IV, e.g., [Gly2]hGLP-2.
In another aspect, the invention provides a method of prophylactically treating a subject at risk of developing an inflammatory condition of the intestine involving the large intestine comprising the steps of
a) identifying a subject at risk of developing an inflammatory bowel condition involving the large intestine; and
b) administering to the subject an amount of GLP-2 or a GLP-2 analog effective to inhibit onset of the inflammatory condition.
In another aspect of the invention, there is provided a method to identify peptides useful to treat inflammatory conditions involving the large intestine comprising the steps of:
a) obtaining an analog of a vertebrate GLP-2 peptide, the analog having at least one amino acid substitution, deletion, addition, or an amino acid with a blocking group;
b) inducing an inflammatory condition of the intestine involving the large intestine in a test animal;
c) treating the test animal having an induced inflammatory condition of the large intestine, with the analog using a regimen capable of eliciting an amelioration of the inflammatory condition of the large intestine when utilized for human [Gl2y]GLP-2; and
d) determining the effect of the analog on the health status or mortality of the test animal compared with control animals not receiving the peptide or determining the mass of the large intestine of test animals compared to control animals not receiving peptide.
In a related aspect of the invention, there is provided a method useful to identify peptides capable of proliferating the tissue of the large intestine comprising the steps of:
a) obtaining an analog of a vertebrate GLP-2 peptide, the analog having at least one amino acid substitution, deletion, addition, or an amino acid with a blocking group;
b) delivering the analog to the large intestine of the test animal using a regimen capable of proliferating the large intestine when utilized for human [Gly2]GLP-2; and
c) assessing the increase in the mass or length of the large intestine after completion of the treatment regime.
In another aspect, the invention provides a method for growing large intestine tissue or cells therefrom, which comprises the step of culturing the tissue or cells in a culturing medium supplemented with a growth promoting amount of GLP-2 or a GLP-2 analog.